Logging in a C# library

Question

What is the best practise regarding logging inside a library?

I am creating a C# library to be used by users and at some points I want to log an error or a warning. Is it a good practice to use log4net and log in a file?

Answer 1

I use log4net in my own library but I would not do this if my library should be used by others (i.e. outside of my organization). In that case I would use an interface for logging, provide a default implementation based on log4net in separate assembly and use one way or another to allow the users of the library to inject their own implementation.

Having said this: I really like log4net and would not use anything else, but I think it is wrong to force others to have to use the logging framework of your choice.

Edit:

• I would also not consider it good practice having the library log to a file by default. The users of your library should be able to decide where log messages end-up.
• I would also provide a "no-operation" implementation that can be used if no logging at all is required. This probably should be default behavior an not require any additional assemblies or steps to implement.